There is hardly a shortage of references to the Agnihotra. The ZB is
primarily concerned with it in 2.1.1--with the Agnyaadhaana through the
actual performance, concluding in 2.4.2. There are several mythological
significations given to contextualize its performance. Frequently these
build upon the notion of the breaths--(thus drawing a need for an e-text
of the JB per Bodewitz' study of the PraaNaagnihotra)--and weave basic links
between the self, the cosmos, the sun, death, Prajaapati and the year.

ZB
2.1.4.10 ff. in the discussion of the Agnyaadhaana, Prajaapati's creation
of the cosmos with "bhuur, bhuuvaH, svaH" (2.1.4.11ff)This explanation is given in answer to the question in .10 as to why
neither Rk, nor saaman, nor yajus, is recited for the
setting up of the fires. The brahmán (m) priest, being speech
and truth, thus establishes the fire. While the notation of accent
seems to indicate udaatta on the first syllable, Weber's edition
follows the mss. in marking anudaatta, thus the accent falls on the
second syllable.

ZB
2.2.1.4f Prajaapati, Agni Pavamaana, and breaths are again asssociated
via svaahaa utterances during these oblations.

ZB
2.2.4.1f tells the basic "idam agra" formulaic creation/sacrificial
explication with agni created from his mouth.

ZB
2.3.3.1f again, Prajaapati creates Agni, but here he is in danger of
burning everything up, so the reproduction and maintenance of the fires
is prescribed.